在EntityType-field中为1：N Doctrine关系选择null值

Question

I got incidents which have a reference to a risk.

I am using Symfony 2.6 and Doctrine ORM entities with the following rather symbolic entities:

class Incident
{
    private $id;
    private $name;
    private $date;
    /**
     * @ORM\ManyToOne(targetEntity="Risk")
     * @ORM\JoinColumn(name="risk_id")
     */
    private $risk;
}

class Risk
{
    private $id;
    private $level;
    private $name;
}

The risks-Table has data like:

id  level   name
1   0       none
2   2       low
3   1       very low
4   5       moderate
5   10      high

For the incidents I got a form-type like this:

class IncidentType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('name')
[...]
            ->add('risk', 'entity', [
                'class' => 'Model:Risk',
                'property' => 'name',
                'empty_data' => null,
                'empty_value' => 'not assessed',
                'expanded' => true,
                'required' => [true|false](see below),
            ])
[...]
}

So my incidents risk can be 'not assessed'. That is when there is no risk set (=null). To keep my model clean I would not want to have a row with a level of -1 and a name of 'not assessed'.

My form works as expected, missing one tiny detail: when the risk is null, my list of radiobuttons has no value selected. This happens regardless of the value of the 'required'-option.

For a null-value I get:

( ) not assessed
( ) none
( ) very low
[...]

I would want:

(x) not assessed
( ) none
( ) very low
[...]

I guess that behaviour is just fine for a (not expanded) drop-down field.

Is there a way to have the 'placeholder'/'empty_value'-option of my radiobuttons selected when the data-value is null?

Answer 1

For your risk field you should do:

class IncidentType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('name')
        [...]
            ->add('risk', 'entity', [
                'class' => 'Model:Risk',
                'property' => 'name',
                'empty_data' => null, 
                'empty_value' => 'not assessed', 
                'expanded' => true, 
                'required' => true
            ])
    [...]
    }
}

I just checked that and it works, the first value is selected when the risk is empty and when using the above code. Note I added 'empty_data' => null, 'empty_value' => 'not assessed', and removed placeholder.